Electromagnetic pickups are used in amplified stringed musical instruments, one example being electric guitars, for the purpose of deriving an electrical signal from vibration of the guitar's strings. This electrical signal is fed to an amplifier and subsequently to a loudspeaker system for conversion to audible sound, thus amplifying the faint sound of the guitars strings into a much louder sound. The aforementioned guitars typically comprise an instrument body having a top face, a neck secured at one end to the instrument body and extending from the instrument body, a number of strings tensioned between anchor points mounted on the neck and a bridge mounted on the top face of the instrument body, and an electromagnetic pickup secured to the top face of the instrument body and positioned close to the string.
One means by which the above electrical signal is derived is an electromagnetic system, comprising, for example, one or more permanent magnets in the core of a coil to provide a magnetic field which encompasses the pickup's sensing coil assembly and extends to the magnetically attractive (for example, ferromagnetic) strings of the instrument.
Another means for generating an electrical signal is one or more coil core pieces made of ferromagnetic material which is not a permanent magnet, but having a separate attendant means of magnetization such as a permanent magnet. The magnetized core pieces attract and channel the magnetic field emanating from the permanent magnet, and divert shape that magnetic field to encompass the pickup sensing coil assembly and to extend to the strings of the instrument. The strings of the instrument are of magnetic steel and attract and vary the magnetic field in response to the vibrations or oscillations of the strings. By the well known electric current generation effect discovered by Michael Faraday in year 1831 this causes any coil of electrically conductive wire that is present in the magnetic field to output electrical signals corresponding and analogous to the strings' vibrations. These electrical signals are then sent to an amplifier and loudspeaker system for reproduction into audible sounds.
Thus, it will be understood that electromagnetic pickups, also known as transducers or sensors pertaining to stringed musical instruments convert mechanical energy of vibrating strings into corresponding electrical energy. As with any electrical generation device guitar transducers have various degrees of efficiency in transducing mechanical energy to electrical energy. There exists certain circumstances that require a high degree of transduction efficiency and there have been various inventions and means to accomplish this. However as electromagnetic pickup technology advances an even greater degree of efficiency is demanded.
One means of increasing efficiency of an electromagnetic pickup is to wind more turns onto the coil, this is known as over-winding. Since only a relatively small electric current is induced into each turn or loop of the coil and the electrical currents are added to each other in a multi-turn coil, it follows that the more turns or loops in the coil the greater the accumulated output is from the coil. Since the number of turns correlates to the electrical output signal, a greater output is derived from adding more turns. In practice, adding more turns also increases the interlayer capacitance effect within the coil and causes sonic degradation by lessening the harmonic content of the signal resulting in loss of clarity and definition.
Another common practice among pickup designers used to increase efficiency of an electromagnetic pickup is to utilize stronger and/or larger magnets than normal, often in conjunction with over-winding the coils. However, excessive magnetism interferes with the vibration pattern of instrument strings causing aberration of musical pitch and results in unmusical discordant frequencies to be present. Excessive magnetism also shortens sustain of string vibrations by attracting the strings into a downward U shaped oscillation path thereby causing strings to collide into the frets of the instrument thereby robbing the strings of energy and causing a corresponding buzzing sound in the signal. This is highly unsatisfactory since musicality of the instrument is severely compromised.
A further means with no attendant sonic degradation of increasing efficiency of an electromagnetic pickup is to dispose the pickup coil assembly into a U shaped channel comprised of a ferromagnetic material such as steel. The magnetic channel attracts and captures magnetic energy that normally radiates far beyond the confines of the pickup and diverts this energy into a semi closed loop from one magnetic pole positioned at the bottom of the coil to the opposite magnetic pole positioned at the top of the coil. The poles being represented at the ends of the permanent magnet in the core of, and perpendicular to the axis of the coil. The open portion of the semi closed loop encompasses the magnetic strings of the guitar thus allowing the magnetic field to grasp the strings, flow through a portion of the strings and return to the opposite end of the permanent magnet. Thus the strings are coupled to a greater degree to the magnetic circuit of the pickup for the purpose of efficiently transducing their mechanical energy to electrical energy.
It is a primary objective of the current invention, a magnetic flux concentrator device, to provide an improved means of increasing the electromagnetic efficiency whereby string vibrations are converted to electrical signals.